The invention resides in a fuel tank for motor vehicles including a venting valve, which automatically closes the tank vent depending on the fuel level in the tank and, by gravity if the motor vehicle is turned upside down.
Such fuel tanks are well known in the art and the venting valves used in connection with such tanks operate quite reliably. They prevent the entering of fuel into the vent line when the vehicle is negotiating curves and also when the vehicle is upside down during a roll-over accident. Although, in fuel tanks, the venting valves are generally arranged in the upper-most part of a tank and a possibly even in dome-like projections, it is difficult to protect the venting system from the results of over-filling the tank. It should be made sure that excessive filling of the tank is prevented and, in due time after completion of the filling procedure, communication is established with the vent system in order, for example, to prevent the tank from being subjected to excess pressures particularly at high ambient temperatures. This should even be true if the tank is filled to an extreme, for example, by the practice of adding in steps small amounts of fuel to "completely fill" the tank. In the tank designs presently in use, such a practice may keep the venting valve closed for an excessive period of time and may lead to an undesirable pressure build up in the tank.
It is the object of the present invention to provide a fuel tank with a venting system, which is not subject to such malfunctions, that is, a venting system, which provides for protection from excessive filling of the tank and which provides for the necessary venting of the tank.